The present invention relates to a computer system; and, more particularly, the invention relates to a method and device for acquiring snapshot data in a storage system for receiving data from an information processing system and for controlling the writing and reading of data to and from a plurality of storage devices, and to a computer system provided with a snapshot acquiring function of this kind.
A computer system is constituted by one or a plurality of information processing devices (hereinafter, also called servers), a data storage system (hereinafter, also called a storage system) for writing or reading data by means of requests from the servers, and various networks connecting these various elements together. In a storage system of this kind, in order to be able to restore the original data from the start of a time period to replace the data updated during that time period, with respect to at least two or more time periods, data (generational data) divided up for each of the respective time intervals is acquired as a snapshot. Specifically, in order to restore the data of a previous time period prior to the time period in which the data has been updated (to restore data of a previous generation), snapshot processing is carried out with respect to the data of the previous time period prior to the data (current generation data) of the time period in which the data is updated by an updating command; and, hence, the data of this time period is acquired as snapshot data and is saved. The data acquired as a snapshot is stored in a prescribed data storage region, in the form of a change (differential data) between the update time period and the time period prior to update, in the same sequence as the time intervals for which the snapshots are acquired, in other words, in a generational order. Patent Japanese Patent Laid-open No. 2002-278819, for example, discloses a method for managing the generation of snapshot data.